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#1492770 - 01/03/2019 17:32 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
EddyG Offline
Meteorological Motor Mouth

Registered: 19/12/2008
Posts: 5506
Loc: Port Stephens NSW
Thats pretty scary stuff now Surly, I believe you guys are on level 3 water restrictions?

I know lake Keepit is all but dry, at about half a percent, what are the other dams sitting at?
_________________________
Rainfall
2018 - 1145.9mm
2019 MTD - 302.7mm
2019 YTD - 631.8mm

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#1492987 - 03/03/2019 16:38 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Hi EddyG
On the Namoi, Keepit Dam, which is the main water storage, is at 0%, and the back-up storage at Split Rock Dam is at 3%. On the Namoi tributary, the Peel River, Chaffey Dam (which supplies Tamworth) is at 30%.
Further north, on the Gwydir River, Copeton Dam is at 12%.

Yes, we are on Level 3 water restrictions. That does not affect me at all.
(1.) Although I built my house in the town (1999), I am not connected directly to town water, but use my 30,000 litre tanks for everything. I have 8,000 litres left. (Almost time to worry.)
(2.) My car doesn't get washed more than once per year, and not every year.
(3.) My garden is practically all plants local to the area, and they need no watering, even in drought.
In the district there has been a widespread die-off of silky oak trees (Grevillea robusta). They are native to the Gold Coast, a more soggy area.
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#1493615 - 09/03/2019 14:21 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Use of groundwater in drought

The drought has been reported from many points of view by the ABC:
https://www.abc.net.au/news/drought/
One report, posted on 2 March 2019, points out that little is known about reserves of groundwater:
https://www.abc.net.au/news/2019-03-02/spike-in-groundwater-use-in-drought-sparks-warning/10850944.

Water users, particularly irrigators, tend to fall back on increased groundwater use when drought makes surface water scarce. Is it being all used up? It seems that we don't know.

The most recent rainfall status graph for Manilla NSW (posted above on 1 March) shows a 10-year rainfall total of only 5826 mm. Had the rainfall in the last ten years been at the average rate of 652 mm per year, the total would have been 6520 mm. The actual rainfall was 694 mm less than that.
That is, total rainfall in the last 10 years has been only 89% of the 136-year average. Do we have as much groundwater in storage as we once had?

That 10-year total is a severe shortage, such as has occurred in less than 5% of history (1946 and 1920, for example). At this time, there are also serious shortages (below the 10th percentile) at the even longer time scales of 12 years, 15 years and 20 years.

Does it matter? Perhaps we are about to find out.
_________________________
Data are cheap; information is expensive!

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#1493647 - 09/03/2019 22:24 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Originally Posted By: Surly Bond
One report, posted on 2 March 2019, points out that little is known about reserves of groundwater:
https://www.abc.net.au/news/2019-03-02/spike-in-groundwater-use-in-drought-sparks-warning/10850944.

A quote from the link had a critical point -- how can someone manage, let alone envisage the future of groundwater / surface water supplies without measurements and monitoring?

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#1495615 - 21/03/2019 11:56 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Inclement Weather Offline
Meteorological Motor Mouth

Registered: 07/03/2006
Posts: 5373
Loc: Diamond Valley
There is some hope on the horizon in looking at a cross-section of the latest runs from the major models. It is showing significant inland troughing after Trevor makes its way inland after crossing the NT coast. It gets picked up by a series of upper troughs and depending on what model you look at, it variously washes out over central Australia, but, significantly some models are having it wash out over the Darling basin. It will be worth keeping an eye on in the coming week.
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#1496188 - 25/03/2019 12:06 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Inclement Weather Offline
Meteorological Motor Mouth

Registered: 07/03/2006
Posts: 5373
Loc: Diamond Valley
The latest forecast for Charleville on the Warego River in the upper reaches of the Darling River look good for some significant rain (100mm plus) into the system for the first time in a long time as a result of ex-TC Trevor.
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The original donut hole

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#1496196 - 25/03/2019 13:26 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Steve777 Offline
Meteorological Motor Mouth

Registered: 20/10/2011
Posts: 5027
Loc: Artarmon (Sydney North Shore)
Here are Sydney's rain numbers for the period April 2018 to March 2019 (Observatory Hill 66062), compared to means and medians for all years.



The last few days of March should not materially affect the result, the pattern or the conclusions. Because of missing data, I used the Comparison site (66214) for June.

The 12 month period started out dry. We had an isolated wet month in June before the Dry returned with a vengeance for the rest of Winter.

The rain returned in Spring, and this actually seems to mark the end of the drought in Sydney. Over 40% of the year's rain fell from October to December. January and February experienced what might be described as "low average" rainfall, a pattern which continued into early March. It's been quite wet since March 13, having rained just about every day since then.

So is the rain back to stay? We'll see.

EDIT: maybe we should change the thread title to be more generic, e.g. "NSW rainfall shortage" (drop May 2018).


Edited by Steve777 (25/03/2019 13:28)

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#1496902 - 01/04/2019 17:16 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
The plot of the severity of rainfall shortages at Manilla at March 2019.

As "Inclement Weather" said was likely, we got some heavy rain at the end of March: 40 mm here.
As this graph shows, that rain affected only the 1-, 2-, and 3-month totals. There had been six extreme shortages on the February graph, and there are still six on the graph for March. I define extreme shortages as totals that are in the lowest 1% of historic rainfall totals. Some shown here are in the lowest 0.1%!
The current extreme shortage in the 7-year rainfall total may not recover to normal in decades. As Steve777 says: "We'll see."
https://climatebysurly.com/2019/03/31/march-rain-leaves-drought-extreme/

Does Sydney currently have significant rainfall deficits in the one to seven year range?
_________________________
Data are cheap; information is expensive!

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#1496985 - 02/04/2019 18:16 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Steve777 Offline
Meteorological Motor Mouth

Registered: 20/10/2011
Posts: 5027
Loc: Artarmon (Sydney North Shore)
Hello SB.

I had a look at the numbers for Sydney (Observatory Hill). I don't think that there are any serious long term deficiencies:
  • For January to March 2019, rainfall has been slightly above average, with a wet March making up for modest shortfalls in January and February.
  • Sydney had 96.5% of its expected rainfall in the 10 years 2009 - 2018. The pattern has been lumpy, with some dry periods lasting two or three months, but it seems to be balancing out with some very wet months, especially in Autumn and early Winter.
  • Every year except 2009 and 2014 received at least 80% of the annual average
  • The driest year was 2014 with 74% of the annual rainfall.
  • The two calendar year period 2017-2018 was somewhat dry, receiving 85% of the rainfall expected over two years.

But that's Sydney, the wind just has to turn onshore and it is likely to rain. We also get rain from Easterly influences like East Coast lows and Easterly troughs. However, only a small amount of rain, if any, from those systems would penetrate beyond the Divide. Even East of the Divide it drops off rapidly with distance from the coast. The situation in, say, Bathurst or even Richmond might not be as rosy.

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#1497023 - 03/04/2019 10:47 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
ashestoashes Offline
Weather Freak

Registered: 22/10/2017
Posts: 739
Loc: Voyager Point (South West Sydn...
Steve do you have any numbers on the rain days and it's deviation from the mean, because I feel it is an important number in terms of evaporation rates and run-off.

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#1497034 - 03/04/2019 19:14 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Andrew-A Offline
Weather Freak

Registered: 11/10/2011
Posts: 251
Loc: Copacabana NSW
Okay egg all over my mug with my 14 hr dry period from this morning prediction.
I’m gunna shut up and let the next 74hr do its thing 😃

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#1497110 - 04/04/2019 18:27 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Steve777 has kindly given some figures for Sydney rainfall in recent months and years as percentages of normal amounts. He considers that the longer-term figures don't show much drought.

I think that the longer-term figures may be rather worse than percentage values suggest. In the driest or wettest of times percentages of normal rainfall rapidly converge on normal as you consider longer periods.
I have plotted out the driest times at Manilla in this graph, which I discussed in my blog here.



As you see, by the time you are considering 10-year (120-month) totals, the record driest 10 years at Manilla (Feb 1937 - Jan 1947) had 86% of normal rainfall. I suspect that Sydney's rainfall is less variable. In that case, perhaps the driest-ever 10 year period in Sydney had more than 90% of normal rainfall. Steve777's observation of 96.5% of normal rainfall in the decade 2009-2018 could be a low value.
Because the percentage of normal rainfall that occurs in droughts rises so rapidly towards normal with increasing duration, the practice of the Bureau of Meteorology is to use the more stable percentile value. That is what is done in the series of drought maps here:
http://www.bom.gov.au/climate/drought/archive/20181003.archive.shtml#tabs=Rainfall-tracker
Unfortunately, those maps show durations only up to 48 months. For the Sydney region, they tend to confirm the observations of Steve777 so far as they go.

Someone should calculate Sydney's rainfall percentile values for the last decade and beyond.
_________________________
Data are cheap; information is expensive!

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#1497118 - 04/04/2019 20:20 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Jimi Offline
Weatherzone Addict

Registered: 15/03/2004
Posts: 1129
Loc: Killara
The question I have is, at what point to long term deficits not matter as much? Does going back ten years really tell us much?

100mm yesterday is more helpful for how the landscape looks now than 100mm a year or longer ago. Similarly, if there was a big drought five years ago which then broke and the following years were reasonably normal, what effects, if any, would the landscape be expected to be showing now even if there was a ten year deficit?

I guess what I'm saying SB is a few good rain events and a better than average year in Manila and a ten year deficit might not matter?

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#1497139 - 05/04/2019 09:50 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Thanks for the question, Jimi.
Water storage over years or decades has become vital as our society has become more centralised and our water use more ambitious.
I don't know, but I imagine that the managers and planners of Sydney water storages must think in terms of water security over very long time periods.
The current crisis in managing the water of the Murray-Darling basin is not something that a wet month or two will resolve.
Long-term rainfall shortage could also be lowering the water-table in ground-water reservoirs. We don't know much about that, and we could get a nasty surprise.
_________________________
Data are cheap; information is expensive!

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#1497308 - 09/04/2019 13:30 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW

This contour graph of rainfall shortages extends the similar graph (above) that ended in January. By March, there are still four durations on the graph that show extreme shortages. While the 18-month total is not now an extreme shortage, the 30-month total is. It is also a driest ever value (1078 mm) shared with October 1966.



https://climatebysurly.com/2019/04/09/rainfall-shortage-sequence-03-2019/
_________________________
Data are cheap; information is expensive!

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#1497591 - 16/04/2019 23:49 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW


This graph shows how the current drought had its origin back in 2012 or earlier, but nobody noticed (especially me).

https://climatebysurly.com/2019/04/16/rainfall-shortage-jan-2000-mar-2019/
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Data are cheap; information is expensive!

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#1497724 - 20/04/2019 14:10 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Use of groundwater in drought - II

I found an interesting relevant CSIRO report covering this topic, specifically about my area:
"Water Availability in the Namoi"
http://www.clw.csiro.au/publications/waterforahealthycountry/mdbsy/pdf/Namoi-Report.pdf

The report was written in 2007, a decade before this drought struck.
Extracts from the Executive Summary:
"The average total surface water resource in the Namoi region is 965 GL/year and on average about 359 GL/year (or 37 percent) of this water is used. This use is comprised of net surface water diversions of 260 GL/year and eventual total streamflow losses induced by groundwater use of 99 GL/year."

That seems to me to be a great reliance on groundwater. That is, 99/(99+260) = 27%! And that is in times when there is normal surface water flow. It is interesting to see how they express it: when groundwater is used, that shows up as less flow in the rivers for use downstream.

"This is a high level of development. Flows in the Namoi River are highly regulated; Split Rock Dam regulates 93 percent of all inflows and Keepit Dam regulates 77 percent of all inflows. Chaffey Dam on the Peel River regulates 41 percent of all inflows."

With Keepit Dam at 1% of capacity and Split Rock Dam at 3%, I don't think that Namoi River flows are "highly regulated" just now.
_________________________
Data are cheap; information is expensive!

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#1498484 - 06/05/2019 23:36 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW


No rain in April also triggered lowest-ever rainfall totals for durations of 15, 18, 24, 30, 72, and 84 months!

https://climatebysurly.com/2019/05/01/april-2019-7-lowest-rainfall-totals/
_________________________
Data are cheap; information is expensive!

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#1498485 - 07/05/2019 00:00 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
The Sydney drinking-water catchment is in shortage, it seems.
https://www.theguardian.com/environment/...ing-record-lows

The article is "shockingly" vague about the actual situation. What can we make of this?
"But on Friday, at a budget estimates hearing, chief executive of New South Wales water David Harriss said that if inflows “continue along the path they’ve been going in the last couple of months” this year’s total amount into the catchment would be only 83 gigalitres."
Whatever could "continue along the path" mean? Constant inflow? With the usual seasonality? With exponential decline?
_________________________
Data are cheap; information is expensive!

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#1498846 - 12/05/2019 17:53 Re: NSW rainfall shortage from May 2018 [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
The dry April takes most of the extreme shortages of 12 to 30 month duration into record-breaking territory.



Explanation here:
https://climatebysurly.com/2019/05/11/rainfall-shortage-sequence-04-2019/
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